Method of processing image and audio information, image and audio processing apparatus and computer program that causes a computer to process image and audio information

ABSTRACT

A method of processing image information in which the image information is encoded by the bit plane and compressed by truncating one or more of the bit planes. Since the index parameter indexing the effect of the truncation on the quality of the image information is generated before the truncation, one can determine the bit planes to be truncated based on the index parameter without decoding the image information.

TECHNICAL FIELD

The present invention generally relates to a method of processing imageand/or audio information, an image and/or audio processing apparatus,and a computer program for processing image and/or audio information.

The present invention more particularly relates to a method ofprocessing image and/or audio information, an image and/or audioprocessing apparatus, and a computer program for processing image and/oraudio information, in which the degrading of the encoded image and/oraudio information caused by the truncation of bit planes can beevaluated without decoding the encoded image and/or audio information.

BACKGROUND ART

The Joint Photographic Experts Group (JPEG) and JPEG 2000 are well knowninternational standards of a method of compressing image data.

FIG. 1 is a schematic diagram for explaining a conventional imageprocessing apparatus that compresses image information by JPEG 2000.When image data 11 are input to an image processing apparatus 12, theimage data 11 are transformed with discrete wavelet transformation (DWT)by a transforming unit 13, are quantized by a quantizing unit 14, areencoded with entropy coding by an encoding unit 15, and are output asencoded data 16. That is, the image information is compressed in themanner in which the image data 11 are transformed into the encoded data16.

In this specification, the “image information” includes the image data11 and any data derived from the image data 11 such as the transformedimage data, the quantized image data, and the encoded image data encodedwith the entropy encoding.

FIG. 2 is a schematic diagram showing a conventional image processingapparatus that decompresses the image information. When encoded data 21are input to an image processing apparatus 22, the encoded data 21 aredecoded with entropy decoding by a decoding unit 23, are reverselyquantized by a reverse quantizing unit 24, are reversely transformedwith reverse discrete wavelet transformation by a reverse transformingunit 25, and are output as image data 26. That is, the imageinformation, the encoded data 21 in this case, is decompressed into theimage data 26.

The image processing apparatus that compresses the image information andthe image processing apparatus that decompresses the image informationare often combined as an image processing system.

The transforming unit 13 will be described by reference to FIGS. 3A and3B. In the case of JPEG 2000, the image data 11 are generally dividedinto tiles 31 as showed in FIG. 3A. Each tile 31 is transformed with DWTas showed in FIG. 3B. FIGS. 3A and 3B illustrate the case in which theimage data 11 are divided into the tiles 31 of 128×128 pixels. If a tile31 of 128×128 pixels is transformed with DWT of level 2, thetransformation generates wavelet coefficient data 32 for three 64×64sub-bands 1LH, 1HL, and 1HH and four 32×32 sub-bands 2LL, 2LH, 2HL, and2HH.

The quantizing unit 14 will be described by reference to FIG. 4. FIG. 4shows an example of formula to be used for quantizing, where “a” and “b”are the wavelet coefficients before and after quantizing, respectively;“|a|” is the absolute value of “a”; “sign(a)” is the sign of “a”; “[ ]”is floor function; and “Δ” is a quantizing step. The wavelet coefficient“a” is quantized to “b” by this formula.

The encoding unit 15 will be described by reference to FIG. 5. In thecase of JPEG 2000, the sub-band 52 of the quantized wavelet coefficientdata 51 is divided into code blocks 53 as showed in FIG. 5A. (If asub-band is larger than a code block, the sub-band is divided into thecode clocks. In the following description, a code block includes asub-band that is not divided into code blocks.)

The code blocks 53 are further divided into bit planes 54 as showed inFIG. 5B. Each bit plane is encoded with entropy encoding such asarithmetic encoding as showed in FIG. 5C. FIG. 5A illustrates the casein which the sub-band 52 is divided into the 4×4 code blocks 53. (Thesize of each code block 53 is 4×4 in this case, but the size is notlimited to 4×4.) FIG. 5B illustrates the case in which the 4×4 codeblock 53 is divided into four bit planes 54. The encoding unit 15encodes with entropy encoding each bit plane 54 of the quantized waveletcoefficient data 51, and outputs the encoded data 16.

In the above description, the image data 11 are assumed to represent amonochrome image. In the case in which the image data 11 represent acolor image, the image data (component) of each color can be input tothe image processing apparatus 12 as showed in FIGS. 6A and 6B. Theimage data represented by RGB format may be directly input to the imageprocessing apparatus 12 as showed in FIG. 6A. The image data representedby RGB format may be converted into another format such as YCbCr formatbefore being input to the image processing apparatus. In the case ofJPEG 2000, the image data represented by the RGB format are generallyconverted into the YCbCr format as showed in FIG. 6B. Since human eyesare not as sensitive to the color difference components (Cb and Cr) asthey are to the brightness component (Y), one can increase datacompression rate by compressing Cb and Cr more than Y.

As described above, in the case of JPEG 2000, the quantized waveletcoefficient data are divided into bit planes, and encoded by the bitplane. If some bit planes are cut off, the image data are furthercompressed. For example, the image data can be compressed by cutting off(truncating) the lower side of the encoded bit planes.

If a compression ratio is given as a target, data are cut off until thecompression ratio reaches the target. If data are cut off, image qualityis degraded. Accordingly, it is necessary to determine, when the dataare cut off to a certain extent, how much the image quality degrades.

According to a method of determining the extent of the degrading showedin “Example and Guideline” (EG) of JPEG 2000, the bit planes aretruncated one by one from the lowest bit plane to the highest bit plane,and the distortion is obtained after each truncation of a bit plane. Forexample, the lowest bit plane is truncated, and the distortion isobtained. Then, the second lowest bit plane is additionally truncated,and the distortion is obtained. This procedure is continued until thehighest bit plane is truncated and the distortion is obtained. Thedistortion is obtained by decoding the encoded data after eachtruncation and comparing the decoded data with the original image data.The distortion is defined as mean squared error (MSE).

Since the encoded data after each truncation are decoded as describedabove, it takes long time to obtain the distortion. Otherwise, hardwarethat accelerates the above procedure is additionally required.

DISCLOSURE OF THE INVENTION

Accordingly, it is a general object of the present invention to providea novel and useful method of processing image data in which one or moreof the above problems are eliminated. A more specific object of thepresent invention is to provide a method of evaluating a distortioncaused by truncation of bit planes without decoding encoded data.

To achieve one of the above problems, a method of processing imageinformation, according to an aspect of the present invention, includesthe step of encoding said image information by a bit plane; the step ofgenerating index parameter indexing degradation of said imageinformation caused by truncation of one or more bit planes based on saidimage information; and the step of compressing said image information bytruncating the bit planes; wherein the bit planes to be truncated aredetermined based on said index parameter.

When truncating the bit planes of the encoded image information, one canevaluate the degradation of the image information caused by thetruncation based on the index parameter generated in advance withoutdecoding the image information.

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an image processing apparatus thatcompresses image information with JPEG 2000;

FIG. 2 is a block diagram showing an image processing apparatus thatdecompresses image information with JPEG 2000;

FIGS. 3A and 3B are schematic diagrams for explaining a transformingunit;

FIG. 4 shows a formula used for a quantizing unit;

FIGS. 5A through 5C are schematic diagrams for explaining an encodingunit;

FIGS. 6A and 6B are schematic diagrams for explaining an imageprocessing apparatus that handles a color image;

FIG. 7 is a block diagram showing an image processing apparatusaccording to an embodiment of the present invention;

FIG. 8 is a schematic diagram showing bit planes and layers;

FIG. 9 is a schematic diagram showing the bit pattern of a layeraccording to an embodiment;

FIG. 10 is a schematic diagram showing the bit pattern of a layeraccording to an embodiment where layers 1 through 3 are truncated;

FIG. 11 is a schematic diagram showing the bit pattern of a layeraccording to an embodiment where layers 1 through 6 are truncated;

FIG. 12 is a schematic diagram showing the bit pattern of a layeraccording to an embodiment where layers 1 through 7 are truncated;

FIG. 13 is a schematic diagram showing the bit pattern of a layeraccording to an embodiment where layers 1 through 8 are truncated;

FIG. 14 is a schematic diagram showing the bit pattern of layers and“Na” and “Nb” of each layer;

FIG. 15 illustrates a bit pattern that gradually changes;

FIG. 16 illustrates a bit pattern that steeply changes;

FIG. 17 illustrates the format of encoded wavelet coefficient data;

FIG. 18 illustrates the configuration of a main header; and

FIG. 19 illustrates the configuration of a tile part header.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description of the preferred embodiments will be described byreference to the drawings.

FIRST EMBODIMENT

FIG. 7 is a block diagram showing an image processing apparatusaccording to an embodiment of the present invention. In FIG. 7, an imageprocessing apparatus 12 is configured by a transforming unit 13, aquantizing unit 14, an encoding unit 15, an index generating unit, acounting unit, 1 distortion predicting unit 73, a slope parameterpredicting unit 74, an index adding unit 75, and a compressing unit 76.The image processing apparatus 12 compresses image data with JPEG 2000.The input image data 11 are transformed with the discrete wavelettransformation by the transforming unit 13, quantized by the quantizingunit 14, encoded with entropy codes by the encoding unit 15, and outputas the encoded data; 16.

FIG. 8 is a schematic diagram showing bit planes 54 and correspondinglayers according to an embodiment of the present invention. As describedabove, the code block 53 of the wavelet coefficient data 51 is dividedinto the bit planes 54. In the case of JPEG 2000, each bit plane isencoded with three paths (coding path) of the entropy code. The group ofcoding paths is called a layer. In this description, the group of codingpaths is assumed to correspond to a layer to make the description easy.That is, it is assumed that the bit plane and a layer correspondingthereto are identical.

The truncation of layers (bit planes) will be discussed below.

FIG. 9 is a schematic diagram showing the bit pattern of layers 1through 12 in the case where the layers 1 through 12 are cut at asurface “A” as showed in FIG. 8. Though a layer is two dimensional, onlyone dimensional bit pattern will be described since the description ofthe one-dimensional case is easier and those skilled in the art willeasily understand the two dimensional case base on the one-dimensionalcase. In FIG. 9, a box is white if the component corresponding theretois ineffective (ineffective bit), and is black if the componentcorresponding thereto is effective (effective bit).

FIG. 10 shows the bit pattern in the case where the layers 1 through 3are truncated. In this case, most of the effective components remainundeleted. FIG. 11 shows the bit pattern in the case where the layers 1through 6 are truncated. In this case, even if the layers 1 through 6are truncated, most of the most significant bits (MSBs) are nottruncated. FIG. 12 shows the bit pattern in the case where the layers 1through 7 are truncated. In this case, more than half data items aredeleted due to the truncation. FIG. 13 shows the bit pattern in the casewhere the layers 1 through 8 are truncated. In this case, most of thedata items are deleted.

FIG. 14 is the same schematic diagram as FIG. 9 except that the numberof MSBs is indicated as “Na” for each layer and the number of MSBs eachfollowed by the second most significant bit that is effective isindicated as “Nb” for each layer. FIG. 14 shows that many MSBs aredistributed at the layer 7.

FIG. 15 and FIG. 16 illustrate other examples of bit patterns. The bitpattern showed in FIG. 15 gradually changes, and the MSBs are widelydistributed over several layers. The bit pattern showed in FIG. 16,however, steeply changes between the bit 7 and 8. The MSBs aredistributed at only layers 1 through 4 and layers 9 through 11.

In the case of FIG. 14, for example, if the layer 7 at which many MSBsare distributed is truncated, the data distribution of the code block ofthe layer substantially changes. That is, the more MSBs are deleted whena layer is truncated, the more the image quality degrades.

As described above, the number of MSBs of each layer is a parameter thatindexes the degrading of the image quality. It is easy to obtain thenumber of MSBs from the wavelet coefficient data. Accordingly, one canevaluate the degrading of an image due to the truncation easily andquickly based on the number of MSBs.

Furthermore, when the bit planes of the encoded data are truncated, thedegrading of an image due to the truncation of bit planes can beevaluated without decoding the encoded data encoded with the entropycode.

For example, if one obtains the number of MSBs of each bit plane inadvance based on the wavelet coefficient data before encoded with theentropy code, and attaches the obtained number of MSBs to the waveletcoefficient data after the entropy encoding or stores the obtainednumber of MSBs in a storing unit, the one can evaluate, without entropydecoding, the degrading of the image due to truncations using theobtained number of MSBs that is attached or stored.

If one predicts the image distortion of the image due to the truncationsof bit planes or a slope parameter (the ratio of the distortion of theimage to the amount of reduced image data by the truncation), andattaches the predicted distortion or slope parameter, instead of theobtained number of MSBs, to the wavelet coefficient data after theentropy encoding or stores the predicted value in the storing unit, theone can evaluate, without entropy decoding, the degrading of the imagedue to the truncations using the predicted distortion or slope parameterthat is attached or stored.

In the following description, the parameters that indicate the degradingof the image due to the truncation of bit planes such as the number ofMSBs of each bit plane, the distortion of the image, and the slopeparameter will be called “index parameter”.

According to the first embodiment, the encoding unit 15 provides theindex generating unit 71 with the wavelet coefficient data 51 beforeentropy encoding (referred to as “wavelet coefficient data 77 beforeentropy encoding”) as showed in FIG. 7. The counting unit 72 provided inthe index generating unit 71 counts the number (Na) of MSBs of each bitplane in the wavelet coefficient data 77 before entropy encoding.

According to the first embodiment, the counting unit 72 provides “Na” tothe distortion predicting unit 73 and the slope parameter predictingunit 74 provided in the index generating unit 71 as showed in FIG. 7.The distorting predicting unit 73 and the slope parameter predictingunit 74 predict the distortion of the image and the slope parameter,respectively, based on “Na” provided from the counting unit 72.

In the case where bit planes 1 through “n” are truncated, the distortionvalue of the image of this case may be defined as the sum of “Na”multiplied by the level of each bit plane. For example, in the case ofFIG. 11, the distortion value of the image is calculated as:0×1+1×2+0×3+1×4+1×5+1×6=17. Accordingly, the slope parameter can bedefined as the ratio of the above distortion value to the amount of datareduced by the truncation.

According to the first embodiment of the present invention, the encodingunit 15 provides the compressing unit 76 with the wavelet coefficientdata 51 after entropy encoding (referred to as “wavelet coefficient data78 after entropy encoding”) as showed in FIG. 7. Additionally, the indexgenerating unit 71 provides the compressing unit 76 with index valuesgenerated in advance such as the obtained “Na” and the predicteddistortion. The compressing unit 76 determines bit planes to betruncated based on the index values provided by the index generatingunit 71, and truncates the determined bit planes.

For example, one may set a predetermined threshold for each bit plane54, and compare the index value generated by the index generating unit71 with the predetermined threshold. The index value of the bit plane 1is compared with corresponding threshold; the index value of the bitplane 2 is compared with corresponding threshold; and so on. If theindex value of the bit plane “n” exceeds corresponding threshold for thefirst time, the bit planes 1 through “n-1” are determined to betruncated. If the index value of the bit plane 1 exceeds correspondingthreshold, that is, n=1, no bit plane is truncated. The thresholds maybe the same, or may be different.

As described above, the compressing unit 76 can determine, withoutentropy decoding, the bit planes to be truncated that does not degradetoo much using the index values generated by the index generating unit71.

According to the embodiment, the encoding unit 15 provides the indexadding unit 75 with the wavelet coefficient data 78 after entropyencoding, and the index generating unit 71 provides the index addingunit 75 with the index values generated in advance as showed in FIG. 7so that the index adding unit 75 can attach the index values to thewavelet coefficient data 78.

After attaching the index values to the wavelet coefficient data 78, theindex adding unit 75 provides the compressing unit 76 with the waveletcoefficient data 78. The compressing unit 76 can determine the bitplanes to be truncated based on the index values attached to the waveletcoefficient data 78 and truncate them.

Accordingly, the compressing unit 76 can determine, without entropydecoding, the bit planes 54 to be truncated using the index valuesattached to the wavelet coefficient data 78 generated by the indexgenerating unit in advance,.and can truncate the determined bit planes.

The wavelet coefficient data 78 after entropy encoding according to JPEG2000 will be described below. FIG. 17 illustrates the format of the“wavelet coefficient data 78 after entropy encoding”. The imageprocessing apparatus showed in FIG. 1 outputs the encoded data 16 ofthis format.

In the case of the image processing apparatus according to theembodiment showed in FIG. 7, the wavelet coefficient data 78 afterentropy encoding are further processed by the compressing unit 76, andare output as the encoded data 16.

In general and in this specification, the term “encoded data” includesnot only the encoded data 16 output by the image processing apparatusbut also the wavelet coefficient data 78 after entropy encoding.

The encoded data of FIG. 17 starts with a main header 171 including“start of codestream” (SOC) 173 and “main” 174 that is the body of themain header 171.

A tile part header 172A follows the main header 171. The tile partheader includes a “start of tile” (SOT) 175A indicating the start of thetile part header 172S, a “tile (A) header maker segment” (T(A)) 176Aindicating the content of the tile part header 172A, and a “start ofdata” (SOD) 177A indicating the start of data.

A bit stream 178A follows the tile part header 172A.

A plurality of tile part headers 172B, 172C, each followed by a bitstream 178B, 178C, . . . , respectively follows the bit stream 178A, ifapplicable. The “end of codestream” (EOC) 179 indicating the end of thecodestream follows the last bit stream.

FIG. 18 illustrates the configuration of the main header 171. Asdescribed above, the main header 171 starts with SOC 173 followed by amarker SIZ (image and tile size) 181 indicating the size. SIZ 181 isfollowed by the following markers in an arbitral order: COD (codingstyle default) 182 required for encoding and decoding, COC (coding stylecomponent) 183, QCD (quantization default) 184 required fro quantizingand reverse quantizing, QCC (quantization component) 185, RGN (region ofinterest) 186, POC (order charge) 187, PPM (packed packet headers) 191,TLM (tile lengths) 192, PLM (packet lengths) 193, CRG (componentregistration) 194, and COM (component) 188, where SIZ, COD, and QCD arerequired but the others are optional.

FIG. 19 illustrates the configuration of the tile part header 172. Thetile part header 172 starts with SOT 175 followed, in any order, by thefollowing markers: COD 182, COC 183, QCD 184, QCC 185, RGN 186, POC 187,PPT (packed packet headers, tile header) 195, PLT (packet lengths, tileheader) 196, and COM 188, where QCD 184 is required and the othermarkers are optional. Then, SOD 177 follows the above markers.

As described above, the index adding unit 75 attaches the index valuesgenerated by the index generating unit 71 to the encoded data of JPEG2000. According to the current format of the encoded data of JPEG 2000,one can insert a comment marker in which the one can store comment textin the encoded data of JPEG 2000. The index values can be stored in thecomment marker. The comment marker may be provided in the main header171 or the tile part header 172. Otherwise, the comment marker may beprovided in a header dedicated for the comment marker.

In the above description, the bit plane of (quantized) waveletcoefficient data is considered. The present invention, however, is alsoapplicable to the bit plane of other image information.

In the above description, the number of MSBs of each bit plane and soforth are used as an index parameter. The present invention, however, isnot limited to those index parameters described above, and can use anyparameter that indexes the degrading of the image due to the truncationof bit planes.

For example, the present invention can use the distortion and/or theslope parameter caused by the truncation of the bit planes using themethods described in the EG of JPEG 2000 as the index parameters. Onecan provide a distortion obtaining unit and/or a slope parameterobtaining unit instead of the counting unit 72 in the image processingapparatus according to the embodiment.

In the above description, it is assumed that the image data arecompressed with JPEG 2000. The present invention, however, is notlimited to JPEG 2000, and is applicable to any other image compressionmethod in which the image information is encoded by the bit plane, andthe encoded image information are compressed by truncating the bitplanes.

Additionally, the present invention is not limited to the case where theimage information is encoded by the bit plane, and the encoded imageinformation is compressed by truncating the bit planes. The presentinvention is also applicable to the case where the image information isencoded part by part, and the each encoded part of the image informationis compressed by reducing the encoded part The present invention is alsoapplicable to audio information such as voice data instead of the imageinformation such as the image data.

SECOND EMBODIMENT

An MSB embodies a half of the amount of information contained in a dataitem. If the second most significant bit (second MSB), that is, the bitsubsequent to the MSB is “1” (effective bit), the MSB and the second MSBholds ½ through ¾, in total, of the amount of information contained inthe data item. If the second MSB is otherwise “0”, the MSB and thesecond MSB hold ¾ through 1 of the amount of information contained inthe data item in total. Accordingly, the distortion of an image can beevaluated more accurately based on not only the number (Na) of MSBs butalso the number (Nb) of MSBs followed by second MSB that is 1. Forexample, one may assume that an MSB followed by a second MSB that is 0is 1.5 times effective on the degrading of the image than an MSBfollowed by a second MSB that is 1, in other words, the MSB followed bya second MSB that is 0 corresponds to 1.5 MSBs followed by a second MSBthat is 1.

When predicting the distortion of an image and the slope parameter, thedistortion predicting unit 73 and the slope parameter predicting unit 74may not necessarily handle all code blocks equally. The distortionpredicting unit 73 and the slope parameter predicting unit 74 may weighteach code block based on the component and the sub band so that thedegrading of the image can be accurately evaluated.

If the encoding unit 15 can compress with entropy encoding the waveletcoefficient data 51 at a compression rate more than desired one, thecompressing unit 76 does not need to truncate the bit planes. Thecompressing unit 76 does not need in this case to attach the index valueto the wavelet coefficient data 51.

The index adding unit 75 attaches the index value to the waveletcoefficient data 51, but can be selectively set, in response to aninstruction from an exterior, not to attach the index value to thewavelet coefficient data 51 so as not to lower the compression rate byattaching the index value unnecessarily.

When a plurality of code blocks in a sub band is truncated at differenttruncation level, the truncation sometimes causes visible distortionbetween the code blocks. To solve this problem, the truncation isgenerally executed by the sub band instead of code block. When thetruncation is executed by the sub band, one can obtain the number ofMSBs by the sub band instead of by the code block so as to reducerequired calculation.

The preferred embodiments of the present invention are described above.The present invention is not limited to these embodiments, but variousvariations and modifications may be made without departing from thescope of the present invention.

This patent application is based on Japanese Laid-open PatentApplication No. 2002-128682 filed on Apr. 30, 2002, the entire contentsof which are hereby incorporated by reference.

Industry Applicability

In the case of JPEG 2000, for example, image information is encoded bythe bit plane, and is compressed by truncating the bit planes of theencoded image information. When truncating the encoded bit planes, onecan evaluate, using the method of processing image information accordingto the present invention, the degrading of the image information causedby the truncation without decoding the encoded image information.

1. A method of processing image information, comprising the steps of:encoding said image information by a bit plane; generating an indexparameter indexing degradation of said image information caused bytruncation of one or more bit planes based on said image information;compressing said image information by truncating the bit planes; andattaching said index parameter to the encoded image information; whereinthe bit planes to be truncated are determined based on the attachedindex parameter.
 2. A method of processing image information, comprisingthe steps of: encoding said image information by a bit plane; generatingan index parameter indexing degradation of said image information causedby truncation of one or more bit planes based on said image information;compressing said image information by truncating the bit planesdetermined based on said index parameter; and counting a number of mostsignificant bits of each bit plane of said image information beforeencoding; wherein said index parameter is said number of mostsignificant bits of each bit plane.
 3. The method as claimed in claim 2,further comprising the step of predicting distortion of said imageinformation caused by the truncation of the bit planes based on saidnumber of most significant bits of each bit plane, wherein said indexparameter contains the predicted distortion.
 4. The method as claimed inclaim 3, further comprising the step of predicting a slope parameter ofsaid distortion of said image information caused by the truncation ofthe bit planes based on said number of most significant bits of each bitplane, wherein said index parameter contains the predicted distortionand the predicted slope parameter.
 5. The method as claimed in claim 1,further comprising the step of obtaining an amount of distortion of saidimage information caused by the truncation of the bit planes based onsaid image information before encoding, wherein said index parametercontains the obtained amount of distortion.
 6. The method as claimed inclaim 5, further comprising the step of obtaining a slope parameter ofsaid distortion of said image information caused by the truncation ofthe bit planes based on said image information before encoding, whereinsaid index parameter contains the obtained amount of distortion and theobtained slope parameter.
 7. The method as claimed in claim 1, whereinsaid image information is compressed with JPEG
 2000. 8. The method asclaimed in claim 1, wherein said image information is compressed withJPEG 2000; and the generated index parameter is stored in a commentmarker of the encoded image information.
 9. The method as claimed inclaim 8, wherein said comment marker is provided in a main header or atile part header of the encoded image information.
 10. An imageprocessing apparatus, comprising: an encoding unit that encodes imageinformation by a bit plane; an index generating unit that generatesindex parameter indexing degradation of said image information caused bytruncation of one or more bit planes based on said image information; acompressing unit that compresses said image information by truncatingthe bit planes; and an index attaching unit that attaches said indexparameter to the encoded image information; wherein the bit planes to betruncated are determined based on the attached index parameter.
 11. Animage processing apparatus, comprising: an encoding unit that encodesimage information by a bit plane; an index generating unit thatgenerates index parameter indexing degradation of said image informationcaused by truncation of one or more bit planes based on said imageinformation; a compressing unit that compresses said image informationby truncating the bit planes determined based on said index parameter;and a counting unit that counts a number of most significant bits ofeach bit plane of said image information before encoding; wherein saidindex parameter contains said number of most significant bits of eachbit plane.
 12. A method of processing image information, comprising thesteps of: encoding said image information by a portion; generating indexparameter indexing degradation of said image information caused bydeletion of one or more portions of said image information; compressingsaid image information by deleting the portions; and attaching saidindex parameter to the encoded image information; wherein the portionsto be deleted are determined based on said index parameter.
 13. An imageprocessing apparatus, comprising: an encoding unit that encodes imageinformation by a portion; an index generating unit that generates indexparameter indexing degradation of said image information caused bydeletion of one or more portions of said image information; acompressing unit that compresses said image information by deleting theportions; and an index attaching unit that attaches said index parameterto the encoded image information; wherein the portions to be deleted aredetermined based on said index parameter.
 14. A computer program thatcauses a computer to process image information, comprising the steps of:encoding said image information by a bit plane; generating indexparameter indexing degradation of said image information caused bytruncation of one or more bit planes based on said image information;compressing said image information by truncating the bit planes; andattaching said index parameter to the encoded image information; whereinthe bit planes to be truncated are determined based on the attachedindex parameter.
 15. A method of processing audio information,comprising the steps of: encoding said audio information by a portion;generating index parameter indexing degradation of said audioinformation caused by deletion of one or more portions of said audioinformation; compressing said audio information by deleting theportions; and attaching said index parameter to the encoded audioinformation; wherein the portions to be deleted are determined based onsaid index parameter.
 16. An audio processing apparatus, comprising: anencoding unit that encodes audio information by a portion; an indexgenerating unit that generates index parameter indexing degradation ofsaid audio information caused by deletion of one or more portions ofsaid audio information; a compressing unit that compresses said audioinformation by deleting the portions; and an index attaching unit thatattaches said index parameter to the encoded audio information; whereinthe portions to be deleted are determined based on said index parameter.17. A computer program that causes a computer to process audioinformation, comprising the steps of: encoding said audio information bya portion; generating index parameter indexing degradation of said audioinformation caused by deletion of one or more portions of said audioinformation; compressing said audio information by deleting theportions; attaching said index parameter to the encoded audioinformation; and wherein the portions to be deleted are determined basedon said index parameter.
 18. A computer program that causes a computerto process image information, comprising the steps of: encoding saidimage information by a portion; generating index parameter indexingdegradation of said image information caused by deletion of one or moreportions of said image information; compressing said image informationby deleting the portions; and attaching said index parameter to theencoded image information; wherein the portions to be deleted aredetermined based on said index parameter.